A power converting device that converts electric power is generally used in well-known electronic apparatuses. The power converting device pulsates, with a full-wave rectifier circuit, an AC voltage from an AC power supply and smoothes a pulsated positive voltage with a capacitor to produce a DC voltage. The power converting device converts the DC voltage into high-frequency pulses by performing switching control. The power converting device includes a primary winding for generating a magnetic field with the high-frequency pulses converted by a converter and a secondary winding excited by the magnetic field generated with the primary winding. The power converting device supplies the converted electric power to a load connected to the secondary winding.
In the power converting device described above, a resistor for discharging the potential of the capacitor for smoothing if supply of electric power from the AC power supply stops is connected in parallel to the capacitor. The resistor is connected in parallel to the capacitor even while the electric power is supplied from the AC power supply and thus a power loss occurs inevitably in the power converting device.